/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.sanselan.formats.png.chunks;

import java.io.IOException;

import org.apache.sanselan.ImageReadException;
import org.apache.sanselan.common.ZLibUtils;
import org.apache.sanselan.formats.png.PngConstants;
import org.apache.sanselan.formats.png.PngText;

public class PNGChunkiTXt extends PNGTextChunk
{
	public final String keyword, text;

	/*
	 * The language tag defined in [RFC-3066] indicates the human language used
	 * by the translated keyword and the text. Unlike the keyword, the language
	 * tag is case-insensitive. It is an ISO 646.IRV:1991 [ISO 646] string
	 * consisting of hyphen-separated words of 1-8 alphanumeric characters each
	 * (for example cn, en-uk, no-bok, x-klingon, x-KlInGoN). If the first word
	 * is two or three letters long, it is an ISO language code [ISO-639]. If
	 * the language tag is empty, the language is unspecified.
	 */
	public final String languageTag;

	public final String translatedKeyword;

	public PNGChunkiTXt(int length, int chunkType, int crc, byte bytes[])
			throws ImageReadException, IOException
	{
		super(length, chunkType, crc, bytes);
		{
			int terminator = findNull(bytes);
			if (terminator < 0)
				throw new ImageReadException(
						"PNG iTXt chunk keyword is not terminated.");

			keyword = new String(bytes, 0, terminator, "ISO-8859-1");
			int index = terminator + 1;

			int compressionFlag = bytes[index++];
			if (compressionFlag != 0 && compressionFlag != 1)
				throw new ImageReadException(
						"PNG iTXt chunk has invalid compression flag: "
								+ compressionFlag);

			boolean compressed = compressionFlag == 1;

			int compressionMethod = bytes[index++];
			if (compressed)
				if (compressionMethod != PngConstants.COMPRESSION_DEFLATE_INFLATE)
					throw new ImageReadException(
							"PNG iTXt chunk has unexpected compression method: "
									+ compressionMethod);
				else if (compressionMethod != 0)
					throw new ImageReadException(
							"PNG iTXt chunk has unexpected compression method: "
									+ compressionMethod);

			terminator = findNull(bytes, index);
			if (terminator < 0)
				throw new ImageReadException(
						"PNG iTXt chunk language tag is not terminated.");

			languageTag = new String(bytes, index, terminator - index,
					"ISO-8859-1");
			index = terminator + 1;

			terminator = findNull(bytes, index);
			if (terminator < 0)
				throw new ImageReadException(
						"PNG iTXt chunk translated keyword is not terminated.");

			translatedKeyword = new String(bytes, index, terminator - index,
					"utf-8");
			index = terminator + 1;

			if (compressed)
			{
				int compressedTextLength = bytes.length - index;
				;
				byte compressedText[] = new byte[compressedTextLength];
				System.arraycopy(bytes, index, compressedText, 0,
						compressedTextLength);

				text = new String(new ZLibUtils().inflate(compressedText),
						"utf-8");

			} else
				text = new String(bytes, index, bytes.length - index, "utf-8");
		}
	}

	/**
	 * @return Returns the keyword.
	 */
	public String getKeyword()
	{
		return keyword;
	}

	/**
	 * @return Returns the text.
	 */
	public String getText()
	{
		return text;
	}

	public PngText getContents()
	{
		return new PngText.iTXt(keyword, text, languageTag, translatedKeyword);
	}
}